The purpose of the study is to determine the safety and clinical benefit of the combinations of abiraterone acetate and prednisone or abiraterone and dexamethasone in prostate cancer patients. Prednisone will be given at one of three different dose schedules. Dexamethasone will be given at one dose schedule. This will include looking at what side effects occur and how often they occur. In addition the impact of the study drug on quality of life and pain will be evaluated. The study will also collect data on subsequent treatment of patients after they come off the study drug (up to a maximum of 5 years after the study starts). By analyzing blood samples, the study aims to identify if some markers could help to understand if the treatment with abiraterone is effective and also help to understand if patients can become resistant.

Further study details as provided by Janssen Pharmaceutica N.V., Belgium:

Primary Outcome Measures:

Number of participants experiencing neither hypokalemia nor hypertension treatment-emergent adverse events up to Week 24 [ Time Frame: up to 24 Weeks after Day 1 of Cycle 1 ] [ Designated as safety issue: Yes ]

Secondary Outcome Measures:

Progression Free Survival [ Time Frame: up to 5 years after the start of study treatment of the first patient in the study ] [ Designated as safety issue: No ]

time from randomization to the occurrence of one of the following: radiographic progression, clinical progression or death

Prostate specific antigen response rate [ Time Frame: up to 5 years after the start of study treatment of the first patient in the study ] [ Designated as safety issue: No ]

A PSA response is defined as a ≥50% decline from baseline according to the adapted PCWG2 criteria. For a PSA response to be confirmed, an additional PSA measurement obtained 4 or more weeks later has to show ≥50% decline from baseline.

Time to prostate specific antigen progression [ Time Frame: up to 5 years after the start of study treatment of the first patient in the study ] [ Designated as safety issue: No ]

Objective response rate [ Time Frame: up to 5 years after the start of study treatment of the first patient in the study ] [ Designated as safety issue: No ]

Time to opiate use for cancer pain [ Time Frame: up to end of main study visit at the end of Cycle 39 (156 weeks) ] [ Designated as safety issue: No ]

Time to deterioration in Eastern Cooperative Oncology Group (ECOG) performance score by 1 point [ Time Frame: up to end of main study visit at the end of Cycle 39 (156 weeks) ] [ Designated as safety issue: No ]

Number of participants with change in EQ-5D-5L score [ Time Frame: Day 1 of Cycles 1, 6, 18, 39 or at end of main study treatment assessment for participants discontinuing study treatment Cycle 39 ] [ Designated as safety issue: No ]

Number of participants with change in Brief Pain Inventory - short form (BPI-SF) score [ Time Frame: Screening; Day 1 of Cycles 1, 6, 18, 39 or at end of main study treatment assessment for participants discontinuing study treatment Cycle 39 ] [ Designated as safety issue: No ]

Number of participants with change in Functional Assessment of Cancer Therapy - Prostate Cancer (FACT-P) score [ Time Frame: Day 1 of Cycles 1, 6, 18, 39 or at end of main study treatment assessment for participants discontinuing study treatment Cycle 39 ] [ Designated as safety issue: No ]

Overall Survival [ Time Frame: up to 5 years after the start of study treatment of the first patient in the study ] [ Designated as safety issue: No ]

Time to next therapy for prostate cancer [ Time Frame: up to 5 years after the start of study treatment of the first patient in the study ] [ Designated as safety issue: No ]

Time to initiation of subsequent chemotherapy [ Time Frame: up to 5 years after the start of study treatment of the first patient in the study ] [ Designated as safety issue: No ]

Treatment duration of subsequent chemotherapy [ Time Frame: up to 5 years after the start of study treatment of the first patient in the study ] [ Designated as safety issue: No ]

Type = exact number; unit = mg; number = 1000; form = tablet; route = oral; taken as four 250 mg tablets once daily at least 2 hours after eating and no food should be eaten for at least 1 hour after taking the tablets.

Drug: Prednisone 5 mg twice daily

type = exact number; unit = mg; number = 5; form = tablet; route = oral; taken twice daily, the first dose in the morning after a meal and the second dose after a minimum interval of 8 hours in the late afternoon or early evening, after a meal

Type = exact number; unit = mg; number = 1000; form = tablet; route = oral; taken as four 250 mg tablets once daily at least 2 hours after eating and no food should be eaten for at least 1 hour after taking the tablets.

Drug: Prednisone 5 mg once daily

type = exact number; unit = mg; number = 5; form = tablet; route = oral; taken once daily, in the morning after a meal

Experimental: AA + prednisone 2.5 mg twice daily

Abiraterone acetate in combination with prednisone 2.5 mg twice daily

Drug: Abiraterone Acetate

Type = exact number; unit = mg; number = 1000; form = tablet; route = oral; taken as four 250 mg tablets once daily at least 2 hours after eating and no food should be eaten for at least 1 hour after taking the tablets.

Drug: Prednisone 2.5 mg twice daily

type = exact number; unit = mg; number = 2.5; form = tablet; route = oral; taken twice daily, the first dose in the morning after a meal and the second dose after a minimum interval of 8 hours in the late afternoon or early evening, after a meal

Experimental: AA + dexamethasone 0.5 mg once daily

Abiraterone acetate in combination with dexamethasone 0.5 mg once daily

Drug: Abiraterone Acetate

Type = exact number; unit = mg; number = 1000; form = tablet; route = oral; taken as four 250 mg tablets once daily at least 2 hours after eating and no food should be eaten for at least 1 hour after taking the tablets.

Have a histologically or cytologically confirmed adenocarcinoma of the prostate Have metastatic disease documented by positive bone scan or by computed tomography or magnetic resonance imaging Have prostate cancer progression documented by prostate specific antigen according to Prostate Cancer Working Group 2 or radiographic progression according to modified RECIST (response evaluation criteria in solid tumors, v1.1) criteria Be asymptomatic from prostate cancer. A score of 0-1 on BPI-SF Question #3 (worst pain in last 24 hours) will be considered asymptomatic Be surgically or medically castrated, with testosterone levels of <50 ng/dL (<2.0 nmol/L). If the subject is being treated with luteinizing hormone releasing hormone (LHRH) agonists or antagonists (subjects who have not undergone orchiectomy), this therapy must have been initiated at least 4 weeks prior to Day 1, Cycle 1 and must be continued throughout the study.

Exclusion Criteria:

Has a history of pituitary or adrenal dysfunction Has an active infection or other medical condition that would contraindicate corticosteroid use Has any chronic medical condition requiring corticosteroid treatment or has received prior corticosteroid treatment for prostate cancer Has a pathological finding consistent with small cell carcinoma of the prostate Has a known brain metastasis

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Please refer to this study by its ClinicalTrials.gov identifier: NCT01867710